1. Field of the Invention
The subject matter of the invention is a metering device for liquids as is used in production shops of industry and also in the laboratory. This metering device is intended and suitable especially for viscous liquids, likewise for liquids which are difficult to meter in some other way. In particular, the metering device for liquids has one or more preferably simultaneous acting metering pumps, and is intended for liquids which are to be metered under sterile conditions.
2. Description of Related Art
The prior art discloses a metering device for liquids (U.S. Pat. No. 4,008,003). This metering device has two metering pumps which can be simultaneously actuated and which are double acting, in the form of so-called positive displacement piston pumps. Each metering pump has a double acting piston and a cylinder which holds and seals the piston with two outside connections per piston end. The connections are connected to one another and to supply and discharge lines.
With such a metering device, it is possible to meter comparatively accurately. However, it is difficult to effectively clean and flush such a metering device with metering pumps built in this manner while still keeping them in an operational state. The complexity of the overall arrangement, and especially, the guidance of a plurality of channels with many corners creates major problems. This is especially difficult when problematic, especially viscous liquids and/or liquids to be metered under sterile conditions are involved. It has been found that these metering devices do not work satisfactorily in practice.
With respect to cleaning or flushing, it is disadvantageous that a flushing liquid can only be conveyed through the system by the pumping action of the positive displacement piston pumps. The cleaning action is therefore quite limited.
Thus, it is an object of the present invention to provide a metering device for liquids, especially for problematic liquids, which is improved in its handling with respect to flushing or cleaning.
This object is achieved in accordance with the invention by a metering device for liquids with one or more preferably simultaneously acting metering pumps being provided with a pump holding plate which supports the at least one metering pump, and a metering channel plate which is parallel to the pump holding plate and has at least one metering channel for the at least one metering pump; wherein the pump holding plate has a flat bottom surface in which the at least one outlet opening of the at least one metering pump is located; wherein the metering channel plate has a top surface which sealingly adjoins the bottom surface of the pump holding plate; wherein, at the sealing surface, a respective outlet opening is adjacent to a respective supply channel; wherein the pump holding plate and the metering channel plate are movable relative to one another; wherein the at least one outlet opening of the at least one metering pump can be selectively overlapped with at least one outlet opening of at least metering channel or at least one supply channel; wherein a respective bypass channel for the at least one metering pump is located in the pump holding plate adjacent to the corresponding outlet opening; and wherein, by the relative displacement of the pump holding plate and the metering channel plate with respect to one another, the at least one outlet opening of the respective bypass channel is movable into a position in which the respective bypass channel connects the at least one respective metering channel to the at least one respective supply channel.
Such a metering device makes it possible to simultaneously meter a plurality of the same liquid volumes into a corresponding number of receiving containers with a plurality of metering pumps which are simultaneously actuated. The metering device for this purpose has a plurality of identical metering pumps which permit simultaneous intake or delivery of a host of the same volumes of liquid. It is desirable that the metering device be cleaned and flushed during operation.
The teaching of the invention can fundamentally be implemented advantageously in a metering device with only one metering pump. In particular, the teaching of the invention can be advantageously implemented with a plurality of integrated metering pumps. In a metering device with several metering pumps, the elimination of external connecting lines between the metering pumps acquires major importance in terms of construction, handling, and cleaning.
According to the invention, the channels of a metering device, which comprises at least one metering pump, are formed in the pump holding plate and the metering channel plate which can form the desired seals at all sites of interest by adjacent sealing surfaces. The distribution of channels on the pump holding plate and the metering channel plate creates the prerequisite for implementing a flow-through system for cleaning the metering device. By means of the bypass channel, specifically with outlet openings in the sealing surface on the bottom of the pump holding plate, the outlet openings of the assigned metering channel and the supply channel can optionally be connected to one another. This enables the possibility of continuous flushing of the channels of the metering device according to the invention. The prerequisite for this is that the metering channel plate, on the top, in fact, has a flat sealing surface which adjoins the bottom of the pump holding plate to form a seal. The continuous flushing of the channels is much more effective in terms of cleaning technology than flushing in the cycle of individual pump strokes, as occurs in the prior art. Moreover, it is interesting that the metering device according to the invention makes it possible to allow the metering pump to work in the flushing position, therefore to effect a flushing flow in the course of pump function.
Structurally, the metering device according to the invention is extremely feasible due to its simple channel routing without bends.
Also, an embodiment of the metering device which acquires special importance is one where, in the position where the bypass channel connects the assigned metering channel to the assigned supply channel, the assigned outlet opening is likewise connected to the metering channel or to the supply channel. In this way, backflushing of the sealing surfaces occurs. This backflushing is of major interest for a plurality of problematic applications, especially for liquids to be metered under sterile conditions.
The invention is explained below using drawings which show embodiments by way of example only.